Need details on 16x2 RGB Backlight negative LCD

by rdevisetti on Sat Dec 22, 2012 8:40 am

Dear Support,

I would like to know how many backlights comes with RGB Backlight negative LCD 16x2 + extras - RGB on black with ID: 399. What is the color of the Backlight LED? Shall we provide +5V supply only to control the intensity of the Backlight, or 3.6V is also enough? Shall we use PWM output to control the intensity?

We would like to use this LCD in our Vehicle Tracking System, and in that we are going to interface this LCD from PSoC 5 Microcontroller from Cypress Semiconductors.

Please also help us to reduce the BOM cost and wiring in interfacing the LCD.

Thanks & Regards,
Raghu Devisetti
Green Ark Enersol Private Limited,
Hyderabad,
India

Ph. +91-8374456783
rdevisetti
 
Posts: 2
Joined: Thu Dec 20, 2012 10:32 am

Re: Need details on 16x2 RGB Backlight negative LCD

by adafruit_support_rick on Sat Dec 22, 2012 12:13 pm

The Technical Details tab on the product page has some of this information. There is also a tutorial page which describes a little more about our character LCDs, including this one.

There is a single RGB LED for the backlight. There are four separate lines (R, G, B, power) for the backlight. The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED. I don't know the specific forward voltages of the LED segments, but RGBs are typically around 2V. With that assumption, the on-board resistors will probably give you around 10mA current draw on 3.6V

You can PWM the RGB control lines using inverse logic (i.e., low = 'ON', high = 'OFF').

You will need 6 digital lines to control the display.
Last edited by adafruit_support_rick on Sat Dec 22, 2012 12:14 pm, edited 1 time in total.
Reason: forgot to include link
User avatar
adafruit_support_rick
 
Posts: 10904
Joined: Tue Mar 15, 2011 10:42 am
Location: Buffalo, NY

Re: Need details on 16x2 RGB Backlight negative LCD

by tldr on Sat Dec 22, 2012 9:05 pm

driverblock wrote:The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED.


are you sure about that? i ask because the shield has current limiting resistors

(hey, lookee there, my captcha is avrT3!)
"If I had known it was harmless, I would have killed it myself." - Phillip K. Dick, A Scanner Darkly
User avatar
tldr
 
Posts: 466
Joined: Thu Aug 30, 2012 12:34 am

Re: Need details on 16x2 RGB Backlight negative LCD

by tldr on Sat Dec 22, 2012 9:12 pm

tldr wrote:
driverblock wrote:
driverblock wrote:The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED.



are you sure about that? i ask because the shield has current limiting resistors


ok. i take it back. after looking at the values used i guess the resistors are there to balance the colors.
"If I had known it was harmless, I would have killed it myself." - Phillip K. Dick, A Scanner Darkly
User avatar
tldr
 
Posts: 466
Joined: Thu Aug 30, 2012 12:34 am

Re: Need details on 16x2 RGB Backlight negative LCD

by adafruit_support_rick on Sun Dec 23, 2012 12:04 pm

@tldr
The product description says this:
The LCD has resistors on board already so that you can drive it with 5V logic and the current draw will be ~20mA per LED.

That's all I know.

You're right about the resistors on the shield. That would have to be a different display that comes with the shield - one that does not have the resistors built-in.
User avatar
adafruit_support_rick
 
Posts: 10904
Joined: Tue Mar 15, 2011 10:42 am
Location: Buffalo, NY

Re: Need details on 16x2 RGB Backlight negative LCD

by adafruit on Mon Dec 24, 2012 2:25 pm

the resistors on the shields are to balance out the colors a bit more, as there is no PWM conotrl.
User avatar
adafruit
 
Posts: 11643
Joined: Thu Apr 06, 2006 3:21 pm
Location: nyc

Re: Need details on 16x2 RGB Backlight negative LCD

by rdevisetti on Tue Dec 25, 2012 7:07 am

Please confirm me that there is only one RGB (Red-Green-Blue) on the LCD Module. We need to control the intensity using the three pins 16, 17 and 18 using 5V input.

But the current flow will be ~14 mA with 3.6 V input, will the intensity be sufficient if we use 3.6 V for the inputs.

Thanks & Regards,
Raghu Devisetti
rdevisetti
 
Posts: 2
Joined: Thu Dec 20, 2012 10:32 am

Re: Need details on 16x2 RGB Backlight negative LCD

by adafruit_support_rick on Tue Dec 25, 2012 2:40 pm

rdevisetti wrote:Please confirm me that there is only one RGB (Red-Green-Blue) on the LCD Module. We need to control the intensity using the three pins 16, 17 and 18 using 5V input.


Yes, that is correct.
rdevisetti wrote:But the current flow will be ~14 mA with 3.6 V input, will the intensity be sufficient if we use 3.6 V for the inputs.


I don't know what you might consider "sufficient" intensity to be. It won't be as bright as 20mA, but it will still work. Logically, it should be roughly equivalent to a 75% duty cycle.
User avatar
adafruit_support_rick
 
Posts: 10904
Joined: Tue Mar 15, 2011 10:42 am
Location: Buffalo, NY